package com.xxl.job.admin.core.route.strategy;

import com.xxl.job.admin.core.route.ExecutorRouter;
import com.xxl.job.core.biz.model.ReturnT;
import com.xxl.job.core.biz.model.TriggerParam;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * 单个JOB对应的每个执行器，使用频率最低的优先被选举 a(*)、LFU(Least Frequently Used)：最不经常使用，频率/次数 b、LRU(Least Recently
 * Used)：最近最久未使用，时间
 * <p>
 * Created by xuxueli on 17/3/10.
 */
public class ExecutorRouteLFU extends ExecutorRouter {

  private static ConcurrentMap<Integer, HashMap<String, Integer>> jobLfuMap = new ConcurrentHashMap<Integer, HashMap<String, Integer>>();
  private static long CACHE_VALID_TIME = 0;

  public String route(int jobId, List<String> addressList) {

    // cache clear
    if (System.currentTimeMillis() > CACHE_VALID_TIME) {
      jobLfuMap.clear();
      CACHE_VALID_TIME = System.currentTimeMillis() + 1000 * 60 * 60 * 24;
    }

    // lfu item init
    HashMap<String, Integer> lfuItemMap = jobLfuMap.get(
        jobId);     // Key排序可以用TreeMap+构造入参Compare；Value排序暂时只能通过ArrayList；
    if (lfuItemMap == null) {
      lfuItemMap = new HashMap<String, Integer>();
      jobLfuMap.putIfAbsent(jobId, lfuItemMap);   // 避免重复覆盖
    }

    // put new
    for (String address : addressList) {
      if (!lfuItemMap.containsKey(address) || lfuItemMap.get(address) > 1000000) {
        lfuItemMap.put(address, new Random().nextInt(addressList.size()));  // 初始化时主动Random一次，缓解首次压力
      }
    }
    // remove old
    List<String> delKeys = new ArrayList<>();
    for (String existKey : lfuItemMap.keySet()) {
      if (!addressList.contains(existKey)) {
        delKeys.add(existKey);
      }
    }
    if (delKeys.size() > 0) {
      for (String delKey : delKeys) {
        lfuItemMap.remove(delKey);
      }
    }

    // load least userd count address
    List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<Map.Entry<String, Integer>>(
        lfuItemMap.entrySet());
    Collections.sort(lfuItemList, new Comparator<Map.Entry<String, Integer>>() {
      @Override
      public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
        return o1.getValue().compareTo(o2.getValue());
      }
    });

    Map.Entry<String, Integer> addressItem = lfuItemList.get(0);
    String minAddress = addressItem.getKey();
    addressItem.setValue(addressItem.getValue() + 1);

    return addressItem.getKey();
  }

  @Override
  public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {
    String address = route(triggerParam.getJobId(), addressList);
    return new ReturnT<String>(address);
  }

}
